1. Field of the Invention
The present invention relates to a voltage regulator; in particular, to a voltage regulator capable of self-startup, an operation method thereof, a voltage regulating system, and a mobile vehicle.
2. Description of Related Art
It is known that car-used alternators can generate electrical power as soon as the engine connected thereto starts. The electrical power generated is further supplied to charge a battery and to power other electrical equipment in the car. In practice, a voltage regulator is used for controlling the operation of the alternator such that the output voltage generated by the alternator can be maintained within a specific operating voltage range.
In brief, a voltage regulator in general is connected to the output terminals of an alternator through a warning lamp and a starter switch. The voltage regulator can operatively receive a current supplied by the warning lamp when the car starts. Specially, the magnitude of current flowing through the rotor coil of the alternator can be adjusted by controlling the operation of a power switch so as to regulate the electric power generated by the alternator. When the output voltage outputted by the alternator is too high, the voltage regulator reduces the on duration in an operation cycle of the power switch to reduce the rotor coil current; when the output voltage outputted by the alternator is too low, the voltage regulator increases the on duration in the operation cycle of the power switch and adjusts the magnitude of the current flowing through the rotor coil so as to adjust the electrical power generated by the alternator. Accordingly, the voltage regulator can be used for stabilizing the output voltage of the alternator so as to ensure the supplied electrical power can be maintained at a sufficient amount such that the electrical equipment in a car can operate normally.
A conventional voltage regulator relies on a 3 W warning lamp powered by a battery to provide a sufficient exciting current exciting the rotor coil so that the alternator to generate electrical power when a car starts. Existing cars have begun to replace 3 watts warning lamp with 2 watts warning lamp or high luminance light emitting diodes (LEDs). Nevertheless, starting the alternator by either using an warning lamp of low wattage or not connect to the warning lamp and just using the internally generated self-exciting current to generate supply current provides insufficient exciting current to the rotor coil causing the alternator unable to operate under low rotational speed. That is, the alternator can only operate with sufficient amount of exciting current to establish voltage and supply power under high rotational speed.